Intraseptal morphine potentiates pentobarbital narcosis and hypothermia in the rat

Morphine injected intraseptally in the amounts of 35 and 70 nmol prolonged pentobarbital-induced narcosis in the rat. Pentobarbital-induced hypothermia was also potentiated by intraseptal injection of 70 nmol of morphine. These effects were antagonized when morphine was injected together with naltrexone (29 nmol). Naltrexone injected by itself into the septum did not significantly affect pentobarbital-narcosis and hypothermia. It is concluded that activation of mu opioid receptors in the septal region could affect the actions of pentobarbital.